Electrical system



Feb. 7, 1950 w. H. NEWELL EAL ELECTRICAL SYSTEM Original Filed April 23,1946 2 Sheets-Sheet l INV ENTORS WLLIAM H.NEWELL HENRY F'.M ENNEY ATTORE umw Feb. 7, 1950 w. H. NEWELL EIAL ELECTRICAL SYSTEM 2 Sheets-Sheet 2Original Filed April 23, 1946 IIIIVI ,00

JIIIIIIIIH nl l 45 fi 54 A mvENfi'oRs WILLIAM H.NEWELL VHENRY F.MQKENNEY TORNEY Patented Feb. 7, 1950 ELECTRICAL SYSTEM William HowardNewcll, New York, and Henry F. McKenney, Flushing, N. Y. assignors toThe Sperry Corporation, a corporation 01' Delaware Original applicationApril 23, 1946, Serial No. 664,206. Divided and this application August14, 1941', Serial No. 768,542

(Cl. I'll-97) 3 Claims.

This invention relates to a system for obtaining a voltage which is aderivative of an alternating voltage of variable amplitude and has foran ohthe above purpose.

Other objects and advantages will be apparent as the nature of theinvention is more fully disclosed.

This application is a division of our copending application for Electricfollow-up system, Serial No. 664,206, filed April 23, 1946, now PatentNo. 2,448,387, dated August 31, 1948.

The invention includes a novel means for obtaining an A. C. voltagewhich is proportional to a derivative of the rate of change of a firstA. (I. voltage. For this purpose the first alternating voltage isconverted into a D. C. voltage which is proportional thereto. The D. C.voltage is differentiated twice by a differentiating network to obtain avoltage which is proportional to the second derivative of the firstvoltage. This latter D. C. voltage is then reconverted to an alternatinvoltage which is likewise proportional to the second derivative of thefirst voltage.

Although the novel features which are believed to be characteristic ofthe invention are pointed out more particularly in the claims appendedhereto, the nature of the invention will be better understood byreferring to the following description taken in connection with theaccompanying drawings in which a specific embodiment thereof is setforth for purposes of illustration.

In the drawings:

Figs. 1 and 2 placed side by side constitute a schematic diagram of asystem embodying the present invention as applied to a follow-up system.

Referring to the drawings more in detail, the incoming signal on linesIll and II is fed to the stators l2 and I3 of synchro receivers H andI5, respectively, having rotors l6 and H which are arranged to bepositioned by a drive shaft l8 through gears l9 and 20, respectively.The gears l9 and 20 are so arranged that the rotor |1 makes severalcomplete revolutions for each revolution of the rotor l6. For example,the rotor |1 may make 36 revolutions for each revolution of the rotorIS.

The synchro receivers II and I are of the usual construction and arearranged so that the voltage in the rotors l6 and I1 vary as a functionof the angular displacement of the rotors from the positions ofcorresponding rotors in the remote synchro transmitters from which theinject to provide a novel and improved system for in correspondence withthe positions of the transmitters a zero voltage is induced therein fromthe stators l2 and i3.

In the embodiment shown the voltage induced in the rotor i1 is suppliedby a line and resistor 26 to the input circuit of an am-,

plifier tube 21. The resistor 26 is provided with a variable tap 28 sothat the voltage applied to the amplifier 21 may be adjusted as desired.This voltage constitutes the A. C. voltage induced in the rotor l1 andcorresponds to the error in position of the fine adjustment receiver 45.The output voltage from the amplifier 21 is fed through resistor 30 andline 3| to a combining network comprising a condenser 32 and resistors33 and 36. The resistor 36 is connected by a line 34 across to the inputch7 cuit of an amplifier tube 35. The resistors 33 and 36 which may beof the order of 1 megohm each constitute in effect a voltage dividernetwork.

The output of the amplifier tube is connected by a line 40 throughcondenser 4| and resistors 42 and 43 to the input circuit of anamplifier tube 44. The output circuit of the amplifier tube 44 issupplied through a condenser 45 and a line 46 to the input circuit of anamplifier tube 50. The input circuit of the amplifier tube 50 isconnected to ground through a pair of resistors 5| and a resistor 52connected in series. A resistor 53 is connected between the cathode ofthe tube 5|) and ground to provide a bias voltage. The common point 54of the resistors 5| is connected by a line 55 to the grid 56 of anamplifier tube 51. The output circuit of the amplifier tube 51 isconnected through condenser 58 and line 59 to the input of an amplifiertube 60. Resistors 6| are connected between the line 59 and the resistor5'2 and form with the resistors 5|, a balancing network.

It will be noted that the output voltage of the amplifier tube 44 isgreater than the input voltage by the gain ratio of the tube and isreversed in phase. The voltage divider resistor 5| is so selected thatthe ratio of the voltage supplied by the line 55 to the grid 56 of theamplifier 51 is inversely proportional to the gain ratio of theamplifier 44 and hence is of the same value as the input voltage to theamplifier tube 44, but differs in phase by from the input voltage to thetube 44. The amplifier tube 51 again reverses the phase of its outputcurrent so that the output of the tube 51 is 180 displaced in phase fromthe output from the tube 44. The above described coming signal isreceived. when the rotors are connections are such that the tubes l4 and51 are caused to operate as push-pull amplifiers. The resistance networkincluding resistors 6| and 52 are used to cause push-pull operation ofthe tubes 44 and 51 and could, of course, be replaced by the push-pullinput transformer to the tubes 44 and 51. The resistance network,however, is more compact and provides a more faithi'ul reproduction ofthe input signal.

The tubes 50 and 60 which are supplied, respectively, by the tubes 44and 51 likewise constitute push-pull amplifiers. For increased power asecond pair 01' tubes 50a and 60a are connected in parallel with thetubes 50 and 60, respectively, the input circuit of the tubes 50a and60a being connected to the lines 46 and 59, respectively, by lines 46aand 69a and resistors 62 and 63. The output circuits of the tubes 50 and60a are connected by lines 65 to a split primary 66 of an outputtransformer 61. The output circuit of the tubes 60 and 60a is connectedthrough a line 68 to the split primary 66. The primary winding 66 may betuned by condensers 69 to the fundamental frequency of the appliedvoltage so as to eliminate or reduce the harmonics and extraneousvoltages. The output transformer 61 is provided with a pair ofsecondaries I0 and II. The secondary I0 is connected through a resistorI2 to ground and a point 73 of the resistor I2 is connected by a line 14and a resistor to the input side of the tube 44 to constitute a negativefeedback which eliminates or suppresses the distortion or pickupvoltages which may be produced by the operation of the amplifiers. Thesecondary II constitutes the output secondary and is connected by leads80 to supply power to a reversible drive motor 8| which is connected todrive the shaft I8. The field of the drive motor 8! is supplied from a115 volt A. C. line 82 by a line 83. The connections of the lines 80 tothe drive motor 8| is such that the drive motor is caused to rotate in adirection to bring the rotor I I to zero voltage position.

The rotor I6 of the coarse receiver is connected by a line 85 to theinput circuit of an amplifier tube 86. The output circuit of theamplifier tube 86 is connected through a condenser 81 and resistor 88 toground and through condenser 61 and a gas tube 89 to the input line 34to the amplifier tube 95 at a point between the resistors 33 and 36. Thearrangement is such that the gas tube 89 is normally inoperative andprevents any voltage from being supplied from the tube 86 to the inputof the tube 35. However, a voltage is developed by the tube 89 which, aspointed out above, is proportional to the error in the position of therotor I6. The connection'is such that when this voltage exceeds apredetermined value corresponding to a predetermined angular error, thegas tube 99 becomes conductive and allows the voltage from the tube 86to be supplied to the input of the amplifier tube 35. The tube 86 thusbecomes a low resistance path in parallel to the high resistance 36 andthus eliminates the eifect of any incoming voltage from the finereceiver on the amplifier 35 and subsequent elements of the circuit. Theamplifier 35 is then virtually under the control of the amplifier 86 andthe succeeding portions of the circuit respond to the signal from thecoarse receiver I4 instead of to signals from the fine receiver I 5.

In order to offset the reverse zero position of the rotor I6 from its180 point for the purpose above mentioned, the rotor I6 is connected bya line 90 to a point 9| in a resistor network comprising resistors 92,thence to ground. The re- 76'- sistors 92 are connected through acondenser 98 and line 94 to a secondary 95 01 a transformer 96 having a.primary 9! connected to the A. C. line 82. The value of the ofisettingvoltage is determined by the position of the point 9| with respect tothe resistors 92 and is so selected that the offsetting voltagecorresponds to about 90 on the fine rotor I! which in the examplechosen, namely 36 to 1 ratio, constitutes 2% degrees movement of thecoarse rotor I6. It is noted that this offsetting voltage is introducedinto the rotor I6 in series with the voltage induced from the stator I2of the receiver I4. The condenser 93 is a phasing condenser to bring theoffsetting voltage into phase with the error voltage in the rotor I6.The rotor I6 is, of course, so positioned with respect to the shaft I'8that its zero voltage position in a forward direction corresponds to thezero voltage position of the rotor II, whereas its zero voltage positionin the reverse direction is offset from the 180 point by an amountdetermined by the'value of the offsetting voltage from the resistors 92as above mentioned.

In order to obtain a braking voltage for the purpose referred to above,an induction generator I00 is connected to be driven by the shaft I8.The field of the generator I00 is supplied by lines IOI with 115 v. fromthe A. C. line 82 through a phasing condenser I02 which is designed tomake the output voltage in phase with the voltage of the A. C. line 82.The output of the in-' duction generator is supplied by a line I03 to abridge circuit comprising a pair of resistors I04 and I0! connected inseries. One end of resistor I04 is connected to the cathode of arectifier tube I06, the anode of which is connected to a wind ing I01constituting a secondary of the transformer 90. The resistor I05 isconnected to the anode of a rectifier tube I 08, the cathode of which isconnected by a line I09 to a winding I I0 likewise constituting asecondary of the transformer 98. The windings H0 and I0! are connectedtogether at III. The point III is grounded through a condenser II2. Itwill be noted that the resistors I04 and I05, rectifiers I06 and I08 andwindings I01 and lit are connected in series circuits so that currentflows therethrough in the direction of the arrows II3. The line I03 isconnected to the common point H4 01 the resistors I04 and I05. Theelements are so chosen that with current flowing through the circuitsderived from the secondaries I 01 and H0, the points III and II 4 are ofequal potential, and no voltage is applied to the condenser IIZ.However, when voltage is supplied to the point II4 by the line' I03 thecurrent flowing through the respective halves of the bridge circuitincluding tubes I06 and I08 becomes unbalanced and a voltage appearsacross the condenser II 2. This voltage across the condenser H2 is inthe form of D. C. voltage which is proportional to the A. C. voltagesupplied to the point II4.

including the tubes I06 and I08, resistors I 04,

I05, secondaries I01 and H0 accordingly convert the applied A. C.voltage to a proportional D. C. voltage.

The high voltage side of the condenser H2 is connected to ground througha condenser I20 and a resistor I2I. The condenser I I2 dischargesthrough the condenser I20 and the resistor I2I at a rate to maintainequilibrium. When the voltage on the condenser H2 is constant, therewill be no current flow through the resistor I2I except for thenegligible leakage current. When, however, the voltage across thecondenser H2 The bridge circuit changes the condenser discharges in asuccession of discharges through the condenser I2! and re-' sistor I 2|until equilibrium is again established. Consequently the current throughthe resstance I2I corresponds to the rate of change of the A. C. voltageapplied by the line I33. Since the voltage supplied by the generator II3 is proportional to the rate or velocity of the sliait II, the voltagedeveloped across the resistor I 2| corresponds to the derivative of thevelocity or acceleration.

The condenser I23 is in turn connected through the condenser I22 and aresistor I 23 to ground. The condenser I22 and resistor I23 act in amanner similar to the condenser I and resistor I to develop a voltageacross the resistor I23 which is proportional to the rate of change ofvoltage across the resistor Hi. This voltage accordingly is proportionalto the rate of change in velocity or to the second derivative of thevelocity oi the shaft i8. The resistor I23 may be replaced orsupplemented by a condenser I23a if desired.

In order to convert this D. C. voltage which represents the secondderivative 0! velocity to a corresponding alternating voltage, a bridgenetwork is provided which comprises tubes I25 and I28, secondaries I21and I28 and resistor network including resistors I30, connected in seriwcircuit so that current will flow through the circuit in the directionof the arrow I3I in response to voltage induced in the secondary coilsI21 and I28. The resistor I23 is connected between a point I32 betweenthe secondaries I21 and HQ and ground, adjustable tap I33 on theresistors I is grounded through a resistor I36. A resistor networkincluding resistors I3$, I35 and I3! is connected across the resistorsI30 and an adjustable tap on the resistor I3! is connected to ground.

A resistor network including resistors I4Ii, I49 and I42 is connectedacross windings I21 and I23 and an adjustable tap I43 on the resistor Iis connected to ground. The adjustable tap I33 oi the resistor I38 isconnected by a line I45 to the input circuit of an amplifier tube I48,the output circuit oi which is connected through a resistor I4? to thecombining network including the condenser 32 and 33.

The bridge circuit including the tubes I25 and I28 is so adjusted bysuitable adjustment of the taps I33 and I31 that with no voltage acrossthe resistor I23 the current flowing through the series circuits due tothe secondaries I21 and I23 is balanced and no voltage appears acrossthe resistor I34. However, when a D. C. voltage is applied to theresistor I23 this balance is upset with the result that an A. C. voltageappears across the resistor I34 which is proportional to the D. C.voltage supplied to the resistor I23. This A. C. voltage appearingacross the resistor I34 is supplied to the amplifier tube I48 and thenceto the combining network to be combined with the control voltage. Thisalternating voltage, which is in phase with the control voltage and isproportional to the second derivative of the velocity of the shaft I3.is introduced into the system in a sense to introduce a braking effecton the drive motor which tends to bring the same to rest. Due to thefact that this voltage is proportional to the rate of change ofacceleration of the drive I motor, it appears only in that portion ofthe cycle of operation during which the drive motor is accelerating ordecelerating as it approaches its zero position.

As pointed out above, the voltage applied to the amplifier 3| isproportional to the angle of error or either the line control receiveror the coarse control receiver. As the zero position is approached thefine control receiver is in control. The amplifiers are so designed thatwhen the voltage supplied by the rotor I1 of the fine receiver is lessthan a predetermined value the amplifier output voltage is proportionalto the applied voltage. When, however, the input voltage exceeds thispredetermined value the ampliiier output voltage remains constant, butis converted to a square wave form. The power amplifier system is sodesigned that this square wave voltage will represent lull voltage forthe driving motor, for example, volts, so that full voltage is suppliedthereto throughout the constant voltage area. In one embodiment, forexample, the rotor Il may develop a half of volt for 30 minutes errorwhich would correspond to about one minute error on the coarse controlrotor I6. Hence a voltage of one volt developed in the rotor I'I wouldcorrespond to an error of about two minutes in the coarse receiver It.The system is preferably designed so that within this one volt range,which corresponds to a two minute error, the response of the amplifier$5 is proportional to the input voltage, but beyond this range theoutput voltage of the amplifier 3% becomes constant and suited whenamplified through the push-pull amplifier stages described above tosupply 115 volts to the driving motor 3i. In this way a full torque isproduced by the driving motor throughout its entire range oi movementbeyond a plus or minus two minute error, and the accel eration anddeceleration must take place during this plus or minus two minutemovement. The braking chest of the second derivative voltage derivedfrom the induction generator lot through the bridge networks abovedescribed is accord ingly utilized to introduce a braking effect whichis propoflional to the rate oi change of acceler-- tion and is designedto the motor to rest within this relatively short plus or minus twominute error range during which the control volt age is proportional toveiooity.

The amplification factor of the amplifiers is limited by the effect oithe voltage at zero posi tion of the fine adjustment rotor which may be01' the order of 0.1 volt and consists of torque producing harmonics andquadrature to cycle components which would tend to overload theamplifier but produce no torque. In the above {15" scribed system anover-all amplification factor of 1 to 115 has been assumed. The constantvolt age range of the system should be as long as poe sible in order tomaintain maximum driving ramciency of the motor. However, the constantvoit age range is limited by the minimum angular range within which themotor can be brought to rest without over-shooting to the oppositeconstant voltage area.

Although a specific embodiment of the inven tion has been shown forpurposes of illustration, it is to be understood that system andcomponent parts thereof are capable 01 various uses and that the scopeor the invention is only to be restricted in accordance with thefollowing claims.

What is claimed is:

1. A system for obtaining a derivative of an alternating voltage ofvariable amplitude, comprising a bridge circuit having outer legsconnected in series, rectifiers in opposite legs arranged for the seriesflow of current in one direction around the bridge, means introducing analternating potential of constant amplitude to a pair of said outerlegs, a diagonal leg connected between ennui points 01' said bridgewhich are of equal potential with respect to the current flow around thebridge produced by said alternating potential, means introducing analternating voltage of variable amplitude into said diagonal leg to acondenser to be charged due to a voltage diflerential produced by andproportional to said last alternating voltage, and a discharge circuitfor said condenser including a resistor across which a direct voltage isdeveloped proportional to the rate of change of said last alternatingvoltage.

2. A system for obtaining a derivative of an alternating voltage ofvariable amplitude, com-y prising a bridge circuit having outer legsconnected in series, rectifiers in opposite legs arranged for the seriesflow of current in one direction around the bridge, means introducing anal-,- ternating potential oi constant amplitude to a pair of said outerlegs, a diagonal leg connected between points of said bridge which areof equal potential with respect to the current flow around the bridgeproduced by said alternating potential, means introducing an alternatingvoltage oi variable amplitude into said diagonal leg to a condenser tobe charged due to a voltage differential produced by and proportional tosaid last alternating voltage, and a discharge circuitfor said condenserincluding a condenser and a resistor in series and a discharge circuitfor said last 0011:.- denser including a condenser and resistor inserice, the voltage drop across said last resistor being proportional tothe first derivative of the rate of change of said last alternatingvoltage.

3. A system for converting a varying direct potential into analternating potential 01 corresponding variable amplitude, comprising abridge circuit including outer legs connected in series, rectifiers inopposite legs connected for the series flow of current in one directionaround the bridge, means introducing an alternating voltage of constantamplitude into said circuit, a diagonal leg connected across points inthe bridge 01' equal potential with respect to the current flow aroundthe bridge due to said last voltage, means introducing into saiddiagonal leg a direct voltage of varying amplitude, and means derivingfrom said diagonal leg an alternating voltage which is proportional tosaid direct voltage.

-. WILLIAM HOWARD NEWELL.

HENRY F. McKENNEY.

asraannons or an The following references are of record in the die ofthis patent:

UNITED STATES PATENTS

